3GPP (Generation Partnership Project) is studying standardization of LTE-advanced as a mobile communication system which becomes a successor of LTE (Long Term Evolution). LTE-advanced has decided to adopt DFT-spread OFDM (DFT-S-OFDM) using DFT (Discrete Fourier Transform) precoding which is also adopted in LTE as an uplink (UL) radio access scheme or SC-FDMA (Single-Carrier Frequency Division Multiple Access).
In LTE UL transmission using SC-FDMA, the following method is adopted as a frequency resource allocation and mapping method of UL physical channel (physical uplink shared channel (PUSCH), physical uplink control channel (PUCCH)) that transmits a data signal and control signal to improve transmission quality while maintaining low PAPR (Peak-to-Average Power Ratio) characteristics of a transmission signal capable of realizing high coverage.
[Regarding PUSCH]
A DFT-spread data signal (or control signal or signal resulting from multiplexing a data signal and control signal) of each terminal apparatus (User Equipment, hereinafter abbreviated as “terminal” or “UE”) is mapped to a continuous frequency band of a PUSCH region in a localized manner.
In addition, a resource allocation method is also available whereby a signal mapped to a continuous frequency band of a PUSCH region is subjected to frequency hopping (inter-slot frequency hopping) between two slots; first-half slot and second-half slot, configured by dividing one subframe into two portions in the PUSCH region.
[Regarding PUCCH]
A control signal spread using a CAZAC (Constant Amplitude Zero Autocorrelation) sequence is subjected to frequency hopping (inter-slot frequency hopping) between two slots; first-half slot and second-half slot, configured by dividing one subframe into two portions in the PUCCH region.
[Regarding PUCCH and PUSCH]
Each terminal does not simultaneously transmit PUSCH for mapping a data signal or the like and PUCCH for mapping a control signal. That is, the PUSCH and PUCCH are not frequency-multiplexed and transmitted. Therefore, a method is adopted whereby when a control signal and data signal are generated simultaneously, both signals are multiplexed into one signal sequence, DFT-spread and mapped to a continuous frequency band of a PUSCH region.
As described above, the frequency resource allocation and mapping method in an LTE UL physical channel (1) maps a signal to a continuous frequency band in a localized manner to thereby maintain a low PAPR characteristic of a UL SC-FDMA signal and (2) use inter-slot frequency hopping, and can thereby improve a frequency diversity effect and an effect of suppressing other cell interference.
For example, Patent Literature 1 discloses an inter-slot frequency hopping method for an uplink physical channel (uplink control channel, uplink shared channel or the like) targeted at a UL SC-FDMA scheme in LTE.
However, due to the influence of limitations to the above-described PUSCH and PUCCH frequency resource allocation and mapping method, there is a problem that flexibility of UL frequency resource allocation is low, and therefore the following method is under study about LTE-advanced UL SC-FDMA transmission (see Non-Patent Literature 1 and Non-Patent Literature 2).
[Regarding PUCCH and PUSCH]
A method of simultaneously transmitting PUSCH for mapping a data signal or the like and PUCCH for mapping a control signal (e.g. L1/L2 control signal). That is, a method of transmitting PUSCH and PUCCH for each terminal through frequency division multiplexing.
FIG. 1 shows an example of time-frequency resource mapping of PUCCH and PUSCH within one subframe by a terminal that frequency division multiplexes and transmits the PUSCH and PUCCH. The PUCCH to which a control signal is mapped frequency-hops at both edges of a system band subjected between slots. On the other hand, the PUSCH to which a data signal or the like is mapped is allocated to continuous resources in the frequency direction and time direction within one subframe in a PUSCH region sandwiched between PUCCH regions, thereby realizing simultaneous transmission of the PUSCH and PUCCH.
When a control signal and data signal are generated simultaneously, this makes it possible to avoid the following problems in the mapping method through an LTE UL physical channel, that is, the method of multiplexing both signals, applying DFT spreading to the signal sequence generated and then mapping the signal sequence to a continuous frequency band of the PUSCH.
That is, when a control signal and data signal are generated simultaneously, the signals are multiplexed and mapped to the PUSCH region, and it is thereby possible to solve the problems that (1) the control signal is not mapped to the allocated PUCCH and therefore the resource utilization efficiency of the PUCCH deteriorates and that (2) the amount of data that can be transmitted with frequency resources of the PUSCH is reduced and the data throughput deteriorates.